3T MRI as a tool for noninvasive biomedical imaging of the body

在脑研究领域，由于信噪比的倍增效应改善了图像，有大量的报道描述了3T MRI相对于1.5T MRI的优势。另一方面，身体的3T磁共振成像一直是具有挑战性的；在空气-非空气界面丰富的身体中，更突出的敏感性伪影，由于射频弱穿透和射频不均匀导致的图像退化，四倍以上的SAR等。然而，相信3T MRI在临床身体成像中具有潜在的强大工具，我们已经处理了两种不同的策略。一是找出高信噪比3T MRI的优势区域，即常规1.5T MRI存在信噪比不足的区域。二是找出减小射频不均匀、SAR增大等不利影响的方法。经过两年的3T体部MRI检查，我们发现3T体部MRI可以提供比1.5T体部MRI更好的图像。如对肝管的详细显示，3T的MRCP优于1.5T。在3T时，HASTE图像的对比度更好。在3T时，我们可以获得良好的子宫颈和卵巢图像。尽管肺内有空气，但3T薄层肺实质图像具有较短的TE，显示了肺实质的详细结构。结合呼吸触发和DTI等其他技术，我们成功地在3T上显示了肾脏的各向异性结构。虽然这些结果是初步的，但这些结果表明，3T MRI可以用来克服我们在1.5T MRI上遇到的困难。

There are numerous reports describing the advantages of 3T MRI over 1.5T MRI in the field of brain research because the doubling effect of SNR improve images. On the other hand, 3T MRI of the body had been challenging ; more prominent susceptibility artifact in the body where air-non air interface is abundant, image degradation caused by weak RF penetration and RF inhomogeneity, four-times greater SAR etc. However, believing that 3T MRI has potentially a powerful tool in clinical body imaging, we have dealt with problem with two different strategies. One is to find out the area where 3T MRI with high SNR is advantageous, i.e.the area conventional 1.5T MRI suffers from shortage of SNR. Another is to find out the ways to reduce the unfavorable effects such as RF inhomogeneity and increase in SAR. After two-years experience of 3T body MRI, we have found that 3T MRI could provide us with images much better than those obtained by 1.5T MRI. For example, MRCP at 3T is superior to 1.5T in the detailed depiction of hepatic duct. Contrast is better at HASTE images at 3T. We could obtain excellent images of the uterine cervix and ovary at 3T. Despite air in lung, thin-slice images of the lung parenchyma at 3T, with short TE, demonstrate detailed structure of the lung parenchyma. And with the combination of other techniques such as respiratory triggering and DTI, we have successfully visualized the anisotropic structure of the kidney much beautifully on 3T. Though preliminary, these results suggest that 3T MRI can be used to overcome the difficulties we have suffered at 1.5T MRI.